In geological exploration or production activities it is frequently desired to utilize rotatable tool elements such as saws, drills and core sampling devices within a bore hole at a considerable distance beneath the surface. The rotatable tool element is usually carried within a sonde or downhole tool and is lowered into the bore hole on the end of a wireline having electrical conductors capable of transmitting electric power to the tool element. When such tool elements are operated in directions perpendicular to the axis of the bore hole and jam while in an extended position, a very serious problem exists. If the jam cannot be cleared and the cutting tool retracted, the downhole tool or sonde cannot be withdrawn from the bore hole without serious damage of destruction.
To be effective a rotatable tool element must not only be rotated but must also be advanced into the material to be cut, drilled or sampled at a rate consistent with the ability of the tool to remove material. The rate of removal of the material varies with the hardness of the material and the condition of the cutting elements. Accordingly, an important object of this invention is to provide an hydraulic apparatus for providing both rotational and translational motion to a tool element, the rate of translational advance of the tool element being automatically maintained to be consistent with the rate of removal of material by the rotating tool element.
When a rotatable tool becomes jammed it ceases to rotate and no longer serves to remove material or rotates so slowly as to be ineffective. When so jammed the tool is usually in an extended position and must be first retracted so that the downhole tool or sonde may be withdrawn from or otherwise moved in the bore hole. The following three modes of unjamming the tool are available:
(1) Discontinue the supply of power for rotating the tool element and apply all available power to retraction thereof. PA1 (2) Continue to supply power for rotation of the tool element in the forward cutting direction and, additionally, supply power for retracting the tool element. PA1 (3) Supply power for rotation of the tool element in the reverse direction and, additionally, supply power for retracting the tool element. PA1 (a) an electric motor driven pump; PA1 (b) a positive displacement hydraulic motor connected by conduit means to the pump and adapted to be driven thereby; PA1 (c) a cutting tool element capable of rotational and translational movement and connected to the hydraulic motor so as to be rotationally drive thereby; PA1 (d) an hydraulic piston interconnected to the cutting tool element so as to impart translational movement thereto as the hydraulic piston is moved; and PA1 (e) conduit means interconnecting the outlet of said hydraulic motor to the hydraulic piston whereby translational advancing movement of the cutting tool element is imparted thereto at a rate which varies with the rate of rotational movement of the cutting tool.
If one of the above modes of unjamming is ineffective either or both of the others can be effective. Moreover, in some cases repeated application of the several modes in different order can be effective. Accordingly, a second important object of this invention is to provide a tool element driving apparatus controllable from the surface for selectively applying any one of the above-described modes of unjamming to a tool disposed in a bore hole.
Another object of this invention is to obtain maximum utilization of the conductors available in a wireline for powering the downhole tool with only a single conductor being required for control purposes in selection of the mode of operation. In a conventional seven conductor wireline this leaves six conductors available for supplying electrical power to the rotating tool and, when the significant IR drop involved when the downhole tool is suspended in very deep bore holes is taken into consideration, this feature is quite significant.
Other objects and advantages of this invention will be apparent to those familiar with the art on reading the following description of the invention.